1. Field of the Invention
The present invention relates to an apparatus for checking and measuring powers, and other optical constants of lenses of spectacles and, more particularly, to an automatic right/left determination apparatus for lenses of spectacles upon checking and measurement executed when lenses are fitted in a frame.
2. Related Background Art
As a conventional right/left determination apparatus for lenses of spectacles equipped in an optical characteristic measurement apparatus for spectacles, the following apparatuses are known: (1) an apparatus which comprises a spectacle frame holding member which can horizontally slide while holding a central bridge portion of a frame of spectacles, and determines a right or left lens upon movement of the spectacle frame holding member; (2) an apparatus in which a pair of right and left microswitches each having a lever-like contact portion are arranged on a contact plate which serves as a reference for determining a right/left position of a lens frame, and a right or left lens is determined upon contact between a temple of spectacles and the contact portion of the right or left microswitch; and (3) an apparatus in which a pair of right and left push buttons such as contact switches are arranged on the contact plate, and a right or left lens is determined upon contact between an eye-rim opposite to a lens present on a measurement optical path, and the push button.
However, in the conventional apparatuses, the following problems are posed. That is, in the right/left determination apparatus (1), the structure is complex, and a mounting operation for setting the bridge portion of the frame of spectacles on the spectacle frame holding member is cumbersome. In the right/left determination apparatus (2), when a lens which is not fitted in a frame of spectacles is measured, the projecting lever-like contact portion of the microswitch disturbs measurement. Even when lenses fitted in the frame are measured, if temples of spectacles extend not to be perpendicular to an eye-rim but to be slightly folded, they cause an erroneous operation. In addition, an erroneous operation may be caused upon contact of a hand or foreign matter.
The right/left determination apparatus (3) has a relatively easy-to-use arrangement as compared to those of the right/left determination apparatuses (1) and (2) However, since eye-rims have various shapes, it is difficult to specify a contact position of a contact plate with respect to an eye-rim. For this reason, some frames of spectacles cannot be subjected to right/left determination. When a large switch is employed to decrease probability of such difficulty in determination, the significance of the contact plate as the reference position is lost. To summarize, the conventional right/left determination apparatuses have complex structures.